In recent years, digital technology-applied information equipment has increasingly enhanced in function and complicated at a rapid pace. As one of user interfaces for facilitating easy access of the user to such digital information equipment, a speech interactive interface is known. The speech interactive interface executes exchange of information (interaction) with the user by voice, to achieve desired manipulation of the equipment. This type of interface has started to be mounted in car navigation systems, digital TV sets and the like.
The interaction achieved by the speech interactive interface is an interaction between the user (human) having feelings and the system (machine) having no feelings. Therefore, if the system responds with monotonous synthesized speech in any situation, the user will feel strange or uncomfortable. To make the speech interactive interface comfortable in use, the system must respond with natural synthesized speech that will not make the user feel strange or uncomfortable. To attain this, it is necessary to produce synthesized speech tinted with feelings suitable for individual situations.
As of today, among studies on speech-mediated expression of feelings, those focusing on pitch change patterns are in the mainstream. In this relation, many studies have been made on intonation expressing feelings of joy and anger. In many of the studies, examined is how people feel when a text is spoken in various pitch patterns as shown in FIG. 29 (in the illustrated example, the text is “ohayai okaeri desune (you are leaving early today, aren't you?)”.